1. Technical Field
The present invention relates to a liquid developer and an image forming device.
2. Related Art
As a developer used for developing an electrostatic latent image formed on a latent image carrying member, there are cited a dry toner having a toner composed of a material including a coloring matter such as a pigment and fixing resin used in a dry condition, and a liquid developer (a liquid toner) having a toner dispersed in an electrical insulating carrier liquid (insulating liquid) as disclosed in JP-A-2006-251253.
A method of using the dry toner has an advantage in handling because a solid toner is handled, but also has a concern of imposing an unfavorable influence of a powder to a human body and so on, and problems in stains caused by a scattered toner, uniformity in the dispersed toner, and so on. Further, in the dry toner, there arises a problem that aggregation of particles easily occurs, which makes it difficult to form toner particles with sufficiently small sizes, thus making it difficult to form a high-resolution toner image. Still further, in the case of forming the toner particles with relatively small sizes, the problems caused by the nature of the powder as described above become further conspicuous.
On the other hand, in the method of using a liquid developer, since the aggregation of the toner particles in the liquid developer is effectively prevented, fine toner particles can be used, and further, the fixing resin with a low softening point (low softening temperature) can be used. As a result, the method of using a liquid developer is provided with features of good reproducibility of fine line images, preferable gray-scale reproducibility, superior color reproducibility, and further a feature of being excellent as a high-speed image forming method.
However, in the liquid developer in the related art, although dispersibility of the toner particles is improved in comparison with dry toners, affinity between the insulating liquid and the toner particles is low, which makes it difficult to maintain a preferable dispersion condition for a long period of time. As a result, it is difficult to assure the shelf life and long-term stability of the liquid developer. Further, there arises a problem that an offset and so on is caused frequently in the fixing process at low temperature corresponding to recent energy saving.